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Hi, I am learning about antennas, and and wondering about how antenna
tuners work. I've read you can use anything as an antenna as long as you
have a tuner. Well, If I put up a wire dipole, and then use a tuner,
what is the best length of wire to use? If I use an 80 meter dipole with
a tuner, is that better than using a 10 meter dipole with a tuner?


Jim
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"James Barrett" wrote in message
. ..
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Hi, I am learning about antennas, and and wondering about how antenna
tuners work. I've read you can use anything as an antenna as long as you
have a tuner. Well, If I put up a wire dipole, and then use a tuner,
what is the best length of wire to use? If I use an 80 meter dipole with
a tuner, is that better than using a 10 meter dipole with a tuner?


Google Antenna tuners

JERD

"JERD" wrote in message
...

"James Barrett" wrote in message
. ..
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Hi, I am learning about antennas, and and wondering about how antenna
tuners work. I've read you can use anything as an antenna as long as you
have a tuner. Well, If I put up a wire dipole, and then use a tuner,
what is the best length of wire to use? If I use an 80 meter dipole with
a tuner, is that better than using a 10 meter dipole with a tuner?


Google Antenna tuners

JERD


http://www.arrl.org/tis/info/Ant-tuner-op.html

http://www.hamuniverse.com/tuner.html

Lamont

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JERD wrote:
"James Barrett" wrote in message
. ..
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Hi, I am learning about antennas, and and wondering about how antenna
tuners work. I've read you can use anything as an antenna as long as you
have a tuner. Well, If I put up a wire dipole, and then use a tuner,
what is the best length of wire to use? If I use an 80 meter dipole with
a tuner, is that better than using a 10 meter dipole with a tuner?


Google Antenna tuners

JERD



I honestly did not think of that. I googled for different variations of
"antenna". I found a web site hamuniverse, and found a very good
description of how an antenna tuner works. So a tuner is really there to
protect the transmitter. You still need the wire cut to frequency if you
want to maximize efficiency and minimize the SWR in the wire. Of course
I am generalizing here. I need the arrl antennabook. ;-)

http://www.hamuniverse.com/tuner.html

Thanks!!

Jim

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James Barrett wrote:
So a tuner is really there to protect the transmitter.

It does that by not allowing reflected energy to
reach the transmitter and redistributing the
reflected energy back toward the antenna as
part of the forward wave. Thus a transmitter can
be sourcing 100 watts while the forward power
on the transmission line is 200 watts.

You still need the wire cut to frequency if you
want to maximize efficiency and minimize the SWR in the wire.

Efficiency can also be maximized by choosing a
near-lossless transmission line. In that case,
SWR doesn't necessarily need to be minimized.
--
73, Cecil http://www.w5dxp.com

"Cecil Moore" wrote in message
...
James Barrett wrote:
So a tuner is really there to protect the transmitter.

It does that by not allowing reflected energy to
reach the transmitter and redistributing the
reflected energy back toward the antenna as
part of the forward wave. Thus a transmitter can
be sourcing 100 watts while the forward power
on the transmission line is 200 watts.

What it really is is an impedance matching network. You adjust the antenna
tuner so that the transmitter sees 50 Ohms. If your SWR meter is calibrated
for 50 Ohms, that means an SWR of 1:1 (between the tuner and the radio).

You still need the wire cut to frequency if you
want to maximize efficiency and minimize the SWR in the wire.

Efficiency can also be maximized by choosing a
near-lossless transmission line. In that case,
SWR doesn't necessarily need to be minimized.
--
You mean the SWR doesn't have to be minimized on the transmission line. If
you don't have a tuner and run a 600 Ohm transmission line into the
transmitter, it will be happy at an SWR of 12:1 if the impedance the
transmitter sees is 50 Ohms. On the other hand, with 600 Ohm line, and an
SWR of 1:1 the transmitter will barf.

The longer wire is usually better than the short. Also, the ARRL recommends
a length that is not resonant on any band to make the job of the antenna
tuner easier. Wires around 100 feet are often used.

Tam/WB2TT

73, Cecil http://www.w5dxp.com

Tam/WB2TT wrote:
"Cecil Moore" wrote in message
It does that by not allowing reflected energy to
reach the transmitter and redistributing the
reflected energy back toward the antenna as
part of the forward wave. Thus a transmitter can
be sourcing 100 watts while the forward power
on the transmission line is 200 watts.

What it really is is an impedance matching network. You adjust the antenna
tuner so that the transmitter sees 50 Ohms. If your SWR meter is calibrated
for 50 Ohms, that means an SWR of 1:1 (between the tuner and the radio).

Yes, and that is a Z0-match to 50 ohms. What happens
at a Z0-match is wave cancellation of reflected waves
through destructive interference which redistributes
the reflected energy back toward the antenna in the
form of constructive interference energy that joins
the forward wave.

micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/waveinteractions/index.html

"... when two waves of equal amplitude and wavelength that are
180-degrees ... out of phase with each other meet, they are not actually
annihilated, ... All of the photon energy present in these waves must
somehow be recovered or redistributed in a new direction, according to
the law of energy conservation ... Instead, upon meeting, the photons
are redistributed to regions that permit constructive interference, so
the effect should be considered as a redistribution of light waves and
photon energy rather than the spontaneous construction or destruction of
light."

The reason that the transmitter is protected is that
the Z0-match *causes* that redistribution of the reflected
energy back toward the antenna. Protecting the transmitter
is a side-effect of tuning the entire antenna *system*
to resonance.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Tam/WB2TT wrote:

What it really is is an impedance matching network. You adjust the
antenna tuner so that the transmitter sees 50 Ohms. If your SWR meter
is calibrated for 50 Ohms, that means an SWR of 1:1 (between the tuner
and the radio).


Yes, and that is a Z0-match to 50 ohms. What happens
at a Z0-match is wave cancellation of reflected waves
through destructive interference which redistributes
the reflected energy back toward the antenna in the
form of constructive interference energy that joins
the forward wave.

Correct, except for the part about destructive interference
redistributing reflected energy. Please note the absence of any such
claim in the cited (or any other) reference.

micro.magnet.fsu.edu/primer/java/scienceopticsu/interference/waveinteractions/index.html


"... when two waves of equal amplitude and wavelength that are
180-degrees ... out of phase with each other meet, they are not actually
annihilated, ... All of the photon energy present in these waves must
somehow be recovered or redistributed in a new direction, according to
the law of energy conservation ... Instead, upon meeting, the photons
are redistributed to regions that permit constructive interference, so
the effect should be considered as a redistribution of light waves and
photon energy rather than the spontaneous construction or destruction of
light."

One addendum:
"Therefore, simple diagrams, such as the one illustrated in Figure 1,
should only be considered as tools that assist with the calculation of
light energy traveling in a specific direction."

The same holds true for the simplified explanation provided by the site.

The reason that the transmitter is protected is that
the Z0-match *causes* that redistribution of the reflected
energy back toward the antenna.

More to the point, the Z-match reflects energy back toward the antenna.

73, ac6xg

Jim Kelley wrote:
Correct, except for the part about destructive interference
redistributing reflected energy. Please note the absence of any such
claim in the cited (or any other) reference.

Please note the presence of constructive interference in
the cited reference: "... the photons are redistributed to
regions that permit constructive interference ...", which
implies an equal magnitude of destructive interference
elsewhere in order to avoid violating the conservation of
energy principle. It is akin to the gain of an antenna.
Constructive interference in one direction is matched
by an equal magnitude of destructive interference in
another direction.

More to the point, the Z-match reflects energy back toward the antenna.

Yes, as "constructive interference" energy which requires
destructive interference elsewhere to balance the
energy equation. Since there are only two directions
available in a transmission line, any constructive
interference toward the load must be balanced by an
equal magnitude of destructive interference toward the
source.

Quoting Reflections II, by Walter Maxwell, page 4-3:
"The destructive wave interference between these two
complementary waves causes a complete cancellation of
energy flow in the direction toward the generator.
Conversely, the constructive wave interference produces
an energy maximum in the direction toward the load,
resulting from the sum of the two reflected waves
and the source wave."

For a non-reflective thin film coating, these two
reflected waves are known as the internal reflection
and the external reflection.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Jim Kelley wrote:

Correct, except for the part about destructive interference
redistributing reflected energy. Please note the absence of any such
claim in the cited (or any other) reference.


Please note the presence of constructive interference in
the cited reference: "... the photons are redistributed to
regions that permit constructive interference ...", which
implies an equal magnitude of destructive interference
elsewhere in order to avoid violating the conservation of
energy principle. It is akin to the gain of an antenna.
Constructive interference in one direction is matched
by an equal magnitude of destructive interference in
another direction.

More to the point, the Z-match reflects energy back toward the antenna.


Yes, as "constructive interference" energy which requires
destructive interference elsewhere to balance the
energy equation. Since there are only two directions
available in a transmission line, any constructive
interference toward the load must be balanced by an
equal magnitude of destructive interference toward the
source.

Quoting Reflections II, by Walter Maxwell, page 4-3:
"The destructive wave interference between these two
complementary waves causes a complete cancellation of
energy flow in the direction toward the generator.
Conversely, the constructive wave interference produces
an energy maximum in the direction toward the load,
resulting from the sum of the two reflected waves
and the source wave."

For a non-reflective thin film coating, these two
reflected waves are known as the internal reflection
and the external reflection.

Physical objects redistribute energy. Interference simply describes
its spacial distribution.

73, ac6xg